Question 162 of 295

In an experiment to measure the focal length $(f)$ of a convex lens, the magnitude of object distance$(x)$ and the image distance$(y)$ are measured with reference to the focal point of the lens. The $y-x$ plot is shown in figure. The focal length of the lens is _____cm.

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Answer: 20

From Newton's formula for lens, we can write
${x}_{1}{x}_{2}={f}^{2} \Rightarrow 20\times 20={f}^{2}$
Therefore, $f=20cm$